Intel 24" iMac 2.66 won't power on!

Hi,

I own a early 2009 Intel 24" Alu iMac 2.66ghz. I was using it the other day and suddenly it went dead. I tried turning it back on - nothing happened. So I changed the power cord and tried it in another room - nothing.

So I found the guide on here and swapped the power supply with a new unit. It didn't fix the problem :(

I was thinking it might be the logic board but surely it would do something if it was this? I get nothing, no fans,noise, nothing.

Any other suggestions on what I could check? Oh, and I did try the SMU reset and reseating the RAM...

if the first led lights ON with GREEN, meaning the power supply(PS) is good, when turning the switch ON, second LED must lit... if its not light it means that the logic board is not receiving any voltages at all, check your SWITCH and the swicth connector to logic board, check also the connection of the PS going to logic board.

I know this is an old topic, but I am having the same issue. At first, I wasn’t getting any diagnostic LED lights at all. I purchased and changed out the power supply and now I get LED#1 on when plugged in. Progress? Upon pressing the power button, nothing happens. No other LEDs come on, no sounds/fans. I went ahead and purchased another logic board, but the same thing is happening with this one too.

I have tested the power switch and it seems to be working. I get continuity between the wires when pushing the button.

My thoughts are that the power supply I purchased is bad, though I don’t know how to test it to verify. Does anyone know of a way to test it (voltage pinout) or have any other idea?

Also, do I need to completely reassemble the system to test it or should I be able to turn it on even without the LCD attached or logic board screws put back in just to see if it does turn on? Not sure if not having all screws back in would prevent it from powering on.